Processing of solid polymer



June 22, 1965 M. E. oLDwElLER ETAL 3,190,867

PROCESSING OF SOLID POLYMER Filed Feb. 26, 1962 Eason Omi mm mummazum Nv mman-xbm ammx INVENTORS.

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U iced States Patent 3,1%,367 PRUCESSlNG @LT SLHD PLYMER Morey E. Oldvfeiler, Whippany, NJ., and Michael A. Moore, Houston, and iliilianl A. Broolrshire, Baytown, Terr., assignors, by direct and mesne assignments, to Esso Research and Engineering Company, Elizabeth, NJ., a corporation of Delaware Filed Feb. 2li, i962, Ser. No; 175,553 l2 Claims (Cl. Eeuw-93.7)

The present invention is directed to a method for processing polymer. More particularly, the invention is concerned with removing nonaqueous solvent from solid polymer of an alpha olefin. In its more specific aspects, the invention is concerned with fluidized processing of Wet nonaqueous solvent-containing solid polymer of an alpha olefin having 2 to 8 carbon atoms in the molecule.

The present invention may be brietly described as a method of processing a wet nonaqueous solvent-contain ing solid polymer of an alpha olefin in which the wet polymer is formed into a disperse phase suspension in a heated gasiform fluidizing medium at an inlet temperature sufhciently high to substantially volatilize the solvent Without melting the polymer. Thus, the temperature of the fiuidizing medium may be above the melting point of the polymer, but the Wet bulb effect of the solvent vaporizing from the polymer protects the polymer from melting. The suspension is flowed through the first zone to remove a major amount of the solvent from the solid polymer and the solid polymer containing a reduced amount of solvent is separated from the suspension and formed into a first dense fluidized bed with a gasiform fluidizing medium at a temperature bclowthe melting point of the polymer to reduce further the solvent content of the polymer. Thereafter, the polymer is formed into a second dense fluidized bed with a heated inert gasiform medium atan inlet temperature substantially the same or slightly higher (about 2 to 15 F., preferably about 2 to l0 F.) than the inlet temperature of the gasiform medium in'iected into the first dense bed to obtain a polymer substantially free of solvent which is recovered. rlfhus, the inlet temperature of the gasiform medium to the second dense bed is not less than the inlet temperature of the first dense bed, but is insufficiently high to melt the polymer.

The polymer which is processed in accordance with the present invention is a polymer of an alpha olefin having 2 to 8 carbon atoms in the molecule and may suitably be exemplified by polyethylene, polypropylene, ethylenepropy-lene copolymers, ethylenebutene-l copolymers, ethylenepentene-l copolymers, and the like, having molecular Weights in the range from about 10,000 to about 1,000,000. These polymers may be produced by polymerization of the corresponding oletins employing the Ziegler type polymerization catalyst which is obtained by at least partially reducing in solution in a diluent a halide of an lamphoteric metal selected from Groups lVB, VB, VlB, and Vlll of the Periodic System of Elementstsee, for example, the Henry D. Hubbard Periodic Chart of the Elements, i947 ed. revised by W. F. Meegers; W. M. Welch Mfg. Co., Chicago, lll.). Examples of suitable halides from which the'catalyst is prepared are the halides of titanium, Zirconiuni,'hafnium, thorium, uranium, vanadium, columbium, tantalum, chromium, molybdenum, tungsten, and mixtures thereof. Exemplary of suitable compounds include titanium tetrachloride, titanium tetrabromide, zirconium tetrachloride, and the like. ther catalysts may be employed to polymerize the alpha olefins.

In preparing catalysts suitable for use in forming the polymer treated in accordance with the present invention,

the amphoteric metal halide is reduced in solution in a nonreactive, nonpolar organic diluent in any suitable manner, such as by means of chemical reaction with a suitable chemical compound having reducing properties, by irradiation, etc. This is done tov reduce at least a portion, and preferably more than about 30 percent of the amphoteric metal halide, to a lower valence state. The product of the reduction step, comprising the diluent and the at least partially reduced amphoteric metal halide, is employed as the medium in which olefin polymerization is eifected.

The dilucnt to be employed should be a nonreactive, nonpolar organic medium in which the amphoteric metal halide starting material is soluble to an extent at least sutlicient to provide an (ll Weight percent solution of amphoteric metal halide starting material. Thus, for example, in preparing the polymerization medium, a 0.1 to l() Weight percent solution of amphoteric metal halide in the diluent may be employed.

Among the diluents that may be employed are saturated aliphatic hydrocarbons, preferably containing from about 5 to l0 carbon atoms per molecule. Specific examples of such diluents include pentane, hexane, heptane, octane, decano, nonane, and mixtures thereof, or other saturated petroleum hydrocarbons. A particularly desirable diluent is n-heptane. lt will be understood that other hydrocarbon diluents may be used, such as aromatic diluen's (benzene, xylene, etc), which are preferred, halogenated aromatic hydrocarbons (monochlorobenzene, dichlorooenzene, etc), gas oil distillate fractions obtained from the catalytic cracking of virgin gas oil feed stocks, diesel oil, etc. lt will be understood that, if desired, mixtures of two or more compatible, miscible diluents may be employed. The diluent should be substantially completely free from oxygen, Water and similar compounds of strong polarity which are reactive with the products obtained by reduction of the amphoteric metal halide.

The nonpolar organic liquid in which the slurry is formed may suitably be identical with the diluent in which the catalyst if formed for polymerizing the olefinic compounds.

The polymerization reaction is suitablyconducted at a temperature in the range from about 60 F. to about 400 F., preferably at about room temperature. Higher tempenatures may be employed, but are generally undesirable in that catalyst decomposition may be encountered. Subatmospheric pressures and pressures up to about 250 atmospheres may be employed in forming the polymer treated in accordance with the present invention. lt is generally preferable to employ in the polymerization technique a comparatively low pressure, and specifically it is desirable to employ atmospheric pressure. Reaction times of about 60 minutes are required, although reaction time may vary Within the range of about l0 minutes to about 24 hours.

ln processing the polymer' of the alpha olefin having 2 to 8 carbon atoms, the polymer is recovered from a slurry as a cake containing an appreciable amount within the range from about 20 percent to about 55 percent by weight of solvent. This wet polymer containing the stated amount of solvent, which may be a mixture of an aromatic hydrocarbon such as xylene and an aliphatic alcohol such as methanol, must then be processed to remove the solvent. The solvents presence is a result of a Washing operation in separating means such as pan filters and centrifugal filters. Washing on the pan lters is designed to remove atactic polymer While the washing operation on the centrifugal filter is designed to remove trace quantities of metals such as catalyst residues as exempl-filed by, but not limited to, titanium and aluminum residues. Other metals may be present depending on the type of catalyst employed but when cocrystallized titanium trichloride-aluminurn chloride is employed, the amount of catalyst residues is reduced by a washing action utilizing Xylene and methanol. Thus, as a specific example, the alpha olen polymer, such as polypropylene, as a wet cake may contain from about 20 percent to about 55 percent by weight of a mixture of 80 parts of methanol and 20 parts by weight of xylene.

The inlet temperatures of the gasiform medium employed in the disperse phase suspension of the present invention may range from about 230 F. to about 330 F. In the rst dense bed, the inlet temperatures of the gasiform medium may range from about 160 F. to about 285 F., while the inlet temperatures of the gasiform medium in the second dense bed may range from about 170 F. to about 300 F.

Operating pressures in the transfer line conduit through which the disperse phase suspension is flowed may range from about atmospheric up to about 100 pounds per square inch gauge. A similar pressure may obtain in the first and second dense beds. It is preferred, however, to employ low pressures in the range from about 2 to about 6 pounds per square inch gauge in the transfer line conduit and a similar pressure in the first dense bed. Preferred pressures in the second dense bed may range from about 1 to about 5 pounds per square inch gauge.

The superficial gas velocity in the disperse phase suspension may range from about 5 to about 75 feet per second with a preferred range from about 20 to about 75 feet per second. The superficial gas velocity in the rst and second dense beds may range from about 0.2 to about 2 feet per second with a preferred range in the first dense bed from about 0.8 to about 1.5 feet per second; whereas, in the second dense bed the superficial gas velocity will preferably range from about 0.4 to about 1.5 feet per second.

The present invention will be further illustrated by reference to the drawing in which:

FIG. 1 is a ow diagram of a preferred or best mode; and

FIG. 2 is a ow diagram of a modification of FIG. 1.

Referring now to the dnawing, numeral 11 designates a charge line by way of which a wet polymer cake, such as the discharge from the centrifugal filter zone of a polypropylene operation, is fed into a feed bin 12, which is an elongated vertical vessel containing a horizontally rotatable leveling means 13 which is carried on a shaft 14, powered by a prime mover 15 through shaft 16 and gears 17. The horizontally rotatable leveling means is arranged above a plurality of screw conveyors 18 which are driven through shaft 19 by a prime mover 20 having a variable speed drive 21. Connected to screw conveyors 18 through discharge conduits 22 is a transfer line or conduit 23 which connects into a separation means 24 fluidly connecting into the top of a vertical elongated vessel 25. Hot gasiform fluidizing medium is introduced into condu-it 23 by way of line 23a into which line 26 connects just ahead of the discharge conduits 22. The separation means 24, which is suitably a cyclone separator, is provided with a conduit 27 depending therefrom and terminating within the vessel 2S. The conduit 27 is provided with a seal such as a star feeder 28 which allows solid polymer separated from the fluidizing medium in cyclone 24 to be discharged into the vessel 25 to form a dense bed 29. Heated gasiform fluidizing medium is introduced by line 30 into vessel 25 below an upwardly open conical foraminous gr-id 31 provided with a plurality of holes for discharge of the hot gasiform fluidizing medium upwardly into the dense bed 29. The dense bed 29 is maintained by level controller 32 connecting by conduits 33 and 34 into the lower and upper ends of the vessel 25 and connected by a line 35 to a suitable valve such as slide valve 36 arranged in the outlet conduit 37, which is a conduit connecting with the conical grid 31. It is to be noted that the outlet conduit 37 is provided with thermal insulation means 38 within the vessel 25. It is also to be noted that the cone forms an angle of about 35 to 50 with the horizontal axis of the vessel 25. An angle of 45 is preferred.

The outlet conduit 37 has a steam lead line 39 controlled by valve 40 for injection of steam into the outlet conduit 37 to assist in the discharge of polymer by line 41 into a second vertical elongated vessel 42. The vessel 42 is provided with a conduit 43 leading into a manifold 44, which discharges into lspiders 45 and 46 in the lower section of the vessel 42. The spiders 45 and 46 are vertically spaced apart and are also vertically spaced between vertically spaced-apart baffle means 47. The lower section of the vessel 42 comprising the spaced-apart spiders 45 and 46 and the baffle means 47 comprise a plurality of stripping stages in the lower section of the vessel 42.

Connected to the upper section of the vessel 42 is a separation means 48, which discharges by a depending conduit 49 through a seal such as star feeder 50 into the vessel 42. The separation means 48, which is suitably a cyclone separator, is connected with the upper portion of the vessel 42 by a discharge conduit S1 which discharges gasiform uidizing medium and entrained dried polymer into the cyclone 48. A conduit 52 discharges fluidizing medium from the cyclone 48.

A dense bed is formed in the plurality of stripping stages in the vessel 42, and the level of this dense bed is controlled by level controller 53 connecting into the lower and upper portions of the vessel 42, respectively, by conduits 54 and 55 and connecting by conduit 56 to a diaphragm valve 57 controlling ilow from the outlet 5S of the vessel 42. The lower portion of the vessel 42 is in the form of a cone 59 for discharge of polymer through the outlet 58, controlled by valve 57. Steam is injected into the conduit 43 from a source not shown, by way of line 60 leading into a trap 61 from whence condensed Water is discharged by line 62. The trap 61 may have a filter means 63 arranged therein to remove foreign bodies. The line 43 connects into the upper end of the trap 61. Line 60 is provided with a valve 64 which controls the iiow of steam through a pressure controller 65 connected by lines 66 and 67 to the trap 6l and the valve 64. A temperature adjusting means such as a cooler 68 is also suitably arranged in the line 60 to adjust the temperature of the steam.

Polymer powder is withdrawn through outlet 58 through valve 57 and is caused to flow through line 70 to a suitable storage bin or to a pelletizing device as may be desired by injecting an inert carrier gas into line 70 by way of line 71.

The iiuidizing medium separated from the polymer in separation zone 24 is withdrawn therefrom by line 72. Line 72 is provided with a temperature sensing means 73, whlch connects by line 74 to the variable speed drive 21. The temperature sensing means 73 senses the temperature of the uidizing medium discharging from separation zone 24 and causes a signal to be transmitted to the variable speed drive 21 and thereby controls the feeding of wet polymer by screw conveyors 18 and conduits 22 into transfer line or conduit 23. The temperature of the gas discharged into line 72 is determined by the dew point of the gas and the degree of solvent removal in line 23. Such temperatures may range from about F. to about F. Lower temperatures may be used if the dew point of the uidizing medium introduced into line 23 is lowered.

Line 72 discharges into a condenser-scrubber means 75 provided in its upper section with vertically spacedapart baftles or contacting means 76. In condenserscrubber 75 a body 77 of condensed solvent is maintained and the level of this condensed solvent is regulated by level controller 78 connected by conduits 79 and 80, respectively, to the lower and upper sections of the vessel 75 and by means of conduit 81 to regulator valve 82 which controls the outlet tlow of solvent. l

The gasiform iluidizing medium in line 72 containing solvent'removed from the polymer in transfer conduit 23 is countercurrently scrubbed with solvent recirculated from the body 77 by line S3, pump $4, line 85 containing a temperature adjusting means such as a cooler 86, and thence by line 87 .through discharge 38 to a point above the baille '76. Make-up solvent may be added to line 85 by branch line 35a, controlled by valve 85h. A purge line S9 in which valve S2 is arranged allows the discharge of excess solvent and maintains the level of the body 77.

Line 90 conducts the gasiform fluidizing medium substantially scrubbed of the solvent content to a blower 91 and thence by Way of line 92 and branch lines 92a and 92b into heaters 93a and 93h where the inlet temperature of the recirculated uidizing medium is raised to the proper point. Line 23a connects into heater 93a, and line 30 connects into the heater 93b.

It may be desirable to add an antioxidant and other inhibitors or stabilizers to the polymer which is recovered by way of line '70. This is conveniently accomplished by injecting a solution of the inhibitor, stabilizer, and/ or antioxidant into the vessel 42. Thus, referring specifically to FIG. 2y a dense bed 42u having a level above the baies 47 has a line 100 leading thereinto. Line 100 may discharge either above or below the level 101 of the dense bed 42a. In FIG. 2, line 100 discharges above the level 101. A source of additives vsuch as inhibitors in an aromatic solution is provided in a vessel 102 from which a line 103 connected to a meter 104leads by line S into a heater 106 to which line 100 connects. An inert gas such as nitrogen is introduced by line 107 into line 10S to carry the solution through the heater 106 and thence by line 100 into the vessel 42 where the solvent is removed and the additive intimately contacted and admixed with the polymer.

y lt will be seen from the description taken with the drawing that a new and simplified mode of removing solvent from polyoleiins and the like has been provided.

This mode and the apparatus by way of which the method is conducted has several important commercial advantages among which are: (1) high onstream service factor; (2) minimum investment; (3) high thermal efciency, thus low operating costs; (4) low polymer holdup and (5) no fouling surfaces; thus, no contamination of product from sloughing olf of degraded material.

By way of explanation, heretofore polymer was dried in rotary driers to reduce the nonaqueous volatiles concentration. Experience has been that the drier tubes become badly fouled. The present invention eliminates the :fouling of the conventional drier equipment.

ln the transfer line or conduit with the screw conveyor leading thereinto, the wet polymer contacts hot gas which suitably is comprised of the vapors of the solvent and a hydrocarbon such as natural gas, including the components thereof such als methane, ethane and propane. Methane is a predominant constituent of natural gas and provision is made for introducting make-up gas into line 90 by line 94, controlled by valve 95. In any event, in the conduit 23 heat .and mass transfer occur rapidly, and the gas is cooled from a temperature which may range from about 230 F. to about 330 F. down to about 115 F. to about 180 F., preferably about 140 F. to about 150 F., which results in a high thermal eiiiciency for the transfer line operation. Thus, the polymer is contacted rapidly and efficiently so that it never exceeds its melting point, the wet bulb effect of the vaporizing solvent protecting the polymer from melting. Thereafter, the polymer of reduced solvent content is recovered from the gas in a cyclone such as 24.

The first fluid bed receives the polymer of reduced solvent contcnt from the first cyclone, and the polymer is contacted in the first fluid bed with the heated sweep gas. Here the polymer is heated further to lower the volatile content to la minimum and again partially cooling the gases which escape into the upper portion of the vessel containing the Iluid bed and forming a second disperse phase which is introduced into the rst disperse phase ahead of and slightly downstream from the entering uidizing gas. In this way, full advantage is taken of the sweep gas to the `first fluid bed to remove further amounts of the volatile matter. The product from the first fluid dense bed is transported to a second dense bed, Where it iS contacted with an inert gas such as steam, although other inert gases such as nitrogen, methane, and the like may be used. The second fluid bed is contacted in a staged vessel having `a plurality of stages with about 2 to 4 actual stages. The temperature in the second dense bed is ordinarily maintained above the dew point of steam if steam is used as the gasiform tiuidizing medium.

in order to illustrate further the present invention, wet polypropylene containing from about 28 percent to 52 percent of a mixture of methanol and Xylenes is fed into a feed bin auch as 12 and is then discharged into a transfer line such as 23 through screw conveyors, such as 18, with bridging prevented in the bin 12 by horizontally rotating leveling means, such as 13.

The wet polymer is fed at a controlled -rate into the transfer line 23 by `a variable speed :screw conveyor controlled by a temperature controller such as has been described in connection with the drawing, which permitsthe outlet temperature of the transfer line to be controlled within i2 F. This control means is quite advantageous, insuring uniform removal of solvent, steady feed rate, and high heat utilization. Smooth and nontouling operation has been obtained in a transfer line with polymer holdup `time varying from about 0.4 to about 1.2 seconds. A preferred holdup time varies from about 0.5 to about 1.0 seconds. Most of the methanol is removed by vaporization inthe lrst 0.1 second, as evidenced byrapid temperature drop of the hot gas after contacting the wet polymer. Thus, the gas introduced by line 23a may be about 320 F., while the gas introduced by line 25 may be about 230 F. with lthe gas discharged into line 72 being about 140 F. The volatile content `of the polymer is reduced from about 20 percent to about 55 percent by weight of the wet polymer down to about 2 percent .to about 15 percent by weight, leaving the equivalent of transfer line 23. Actually, in this operation the volatile content may be from about 5 to about 13 weight percent. With the dense bed 2L@ at about 230 F. with .a residence time of about l0 minutes, the polymer volatile content introduced into vessel 42 is about 0.5 percent or within the range from about 0.05 percent to about 1.5 percent by weight. The dense bed in vessel a2 is at a temperature of about 240 F., and the residence time is about 12 minutes with the polymer product discharged by line 70 containing less than 100 ppm. of solvent, usually less than 50 p.p.m. The steam used as an inert iiuidizing medium in vessel 42 may be at an inlet temperature of about 290 F., although other ternperatures may be used.

In an operation wherein a foraminous grid such as 3l is employed, a perforated con-ical grid sloping at 45 to the center has given satisfactory operations at 275 F. gas inlet temperatures. There is no tendency for the polymer to circulate through the 1/s-inch holes in the conical grid during operation, and the polymer is discharged through the outlet 37 with-out diiiiculty.

In an `operation such as described with respect to FIG. 1, dense bed levels such as in vessels 25 and 42 have been easily maintained by level controllers such as have been described.

Operating data show that `the polymer such as introduced by line 41 contain-ing 0.5 weight percent of solvent may be reduced to 50 ppm. of solvent in a vessel such as 42 wherein less than 15 minutes holdup is required. This may be compared with steam-heated rotary driers which ordinarily require two hours holdup to reduce volatile content to these levels. Holdup time in the rst disperse phase and first dense bed is about 10 minutes as compared to the usual 30 minutes required by the conventional rst stage rotary operation.

It will be seen from the foregoing description taken with the drawing `that a new and improved process has been provided for handling wet solid polymer of an alpha olefin. It has also been shown that numerous advantages inure to the present invention.

The nature and objects of the present invention having been completely described and illustrated and the best mode thereof set forth, what we wish to claim as new and useful and secure by Letters Patent is:

1. A method of processing a wet non-aqueous solventcontaining solid polymer of an alpha-olefin having 2 to 8 carbon atoms in the molecule, said Wet polymer containing from about to 55% by weight of solvent, which comprises introducing said wet polymer into an elongated transfer zone, forming a first disperse phase suspension of said polymer in said transfer zone in a heated gasiform fiuidizing medium comprising a hydrocarbon at a temperature within the range from about 230 F. to about 330 F. and iiowing said suspension in said disperse phase at a superfiicial gas velocity from about 5 to about 75 feet per second through said transfer zone and thereby maintaining said polymer below its melting point and removing solvent therefrom, separating said suspension into solid polymer containing from about 2% to about 15% by weight of solvent and gasiform uidizing medium, forming said separated polymer into a dense uidized bed with a heated gasiform tiuidizing medium comprising a hydrocarbon at a temperature below the melting point of the polymer and within the range from about 160 F. to about 185 F. at a superticial gas velocity from about 0.2 to about 2 feet per second, to reduce further the solvent content of said polymer to about 0.05% to about 1.5% by weight, forming a second disperse phase above said first dense bed and introducing said second disperse phase into said heated gasiform uidizing medium forming said first disperse phase suspension, withdrawing said reduced solvent-containing polymer from said iirst dense bed and forming said withdrawn reduced solvent-containing polymer into a second dense fiuidized bed with a heated inert gasiforrn medium at a temperature below the melting point of the polymer and higher than the temperature of the heated gasiform medium introduced into the first dense bed within the range from about 170 F. to about 300 F. at a superficial gas velocity from about 0.2 to about to about 2 feet per second to reduce the solvent content of the polymer to less than 100 p.p.m. and recovering said polymer from said second fluidized bed.

2. A method in accordance with claim 1 in which the temperature of the heated inert gasiform medium introduced into the second dense bed is about 2 F. to 15 F.

dium introduced into the first dense bed.

3. A method in accordance with claim 1 in which the alpha olefin is ethylene.

4. A method in accordance with claim 1 in which the alpha olefin is propylene.

5. A method in accordance with claim 1 in which the heated gasiform fiuidizing medium employed in the first zone is a normally gaseous hydrocarbon.

6. A method in accordance with claim 1 in which the heated gasiform fluidizing medium employed in the first zone and in the first dense bed is a normally gaseous hydrocarbon.

7. A method in accordance with claim 1 in which the heated inert gasiform medium comprises water vapor at a temperature above its dew point.

8. A method in accordance with claim 1 in which the heated gasiform medium employed in the first zone and in the rirst dense bed comprises vapors of said solvent.

9. A method in accordance with claim 3 in which the solvent is a mixture of an aliphatic alcohol and an aromatic hydrocarbon.

10. A method in accordance with claim 1 in which the introduction of said wet polymer into said transfer zone is controlled by the temperature of the separated gasiform uidizing medium.

11. A method in accordance with claim 1 in which the second dense bed comprises a plurality of stages into which said heated inert gasiform medium is separately introduced.

32. A method in accordance with claim 1 wherein the polymer is polypropylene, the heated gasiform fluidizing medium employed in said first Zone and in said first dense bed comprises vapors of said solvent, and the heated inert gasiform medium is water vapor at a temperature above its dew point.

References Cited by the Examiner UNITED STATES PATENTS 2,918,461 12/59 Flynn 260-94-9 2,964,513 12/60 Dale 260--94-9 3,031,769 5/62 Wilson 34-57 3,036,055 5/ 62 Greenwell 260-93.7 3,037,011 5/62 Leibson et al 260-93.7 3,040,438 6/62 Perlman et al 34-57 3,052,990 9/62 Tailor 34-57 3,073,810 1/63 Ross 260-94.9

FOREIGN PATENTS 618,477 4/ 61 Canada.

JOSEPH L. SCHOFER, Primary Examiner. 

1. A METHOD OF PROCESSING A WET NON-AQUEOUS SOLVENTCONTAINING SOLID POLYMER OF AN ALPHA-OLEFIN HAVING 2 TO 8 CARBON ATMS IN THE MOLECULE, SAID WET POLYMER CONTAINING FROM ABOUT 20% TO 55% BY WEIGHT OF SOLVENT, WHICH COMPRISES INTRODUCING SAID WET POLYMER INTO AN ELONGATED TRANSFER ZONE, FORMING A FIRST DISPERSE PHASE SUSPENSION OF SAID POLYMER IN SAID TRANSFER ZONE IN A HEATED GASIFORM FLUIDIZING MEDIUM COMPRISING A HYDROCARBON AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT 230*F. TO ABOUT 330*F. AND FLOWING SAID SUSPENSION IN SAID DISPERSE PHASE AT A SUPERFICIAL GAS VELOCITY FROM ABOUT 5 TO ABOUT 75 FEET PER SECOND THROUGH SAID TRANSFER ZONE AND THEREBY MAINTAINING SAID POLYER BELOW ITS MELTING POINT AND REMOVING SOLVENT THEREFROM, SEPARATING SAID SUSPENSION INTO SOLID POLYMER CONTAINING FROM ABOUT 2% TO ABOUT 15% BY WEIGHT OF SOLVENT AND GASIFORM FLUIDIZING MEDIUM, FORMING SAID SEPARATED POLYMER INTO A DENSE FLUIDIZED BED WITH A HEATED GASIFORM FLUIDIZING MEDIUM COMPRISING A HYDROCARBON AT A TEMPERATURE BELOW THE MELTING POINT OF THE POLYMER AND WITHIN THE RANGE FROM ABOUT 160*F. TO ABOUT 185*F. AT A SUPERFICIAL GAS VELOCITY FROM ABOUT 0.2 TO ABOUT 2 FEET PER SECOND, TO REDUCE FURTHER THE SOLVENT CONTENT OF SAID POLYMER TO ABOUT 0.05% TO ABOUT 1.5% BY WEIGHT, FORMING A SECOND DISPERSE PHSE ABOVE SAID FIRST DENSE BED AND INTRODUCING SAID SECOND DISPERXE PHASE INTO SAID HEATED GASIFORM FLUIDIZING MEDIUM FORMING SAID FIRST DISPERSE PHASE SUSPENSION, WITHDRAWING SAID REDUCED SOLVENT-CONTAINING POLYMER FROM SAID FIRST DENSE BED AND FORMING SAID WITHDRAWN REDUCED SOLVENT-CONTAINING POLYMER INTO A SECOND DENSE FLUIDIZED BED WITH A HEATED INERT GASIFORM MEDIUM AT A TEMPERATURE BELOW THE MELTING POINT OF THE POLYMER AND HIGHER THAN THE TEMPERATURE OF THE HEATED GASIFORM MEDIUM INTRODUCED INTO THE FIRST DENSE BED WITHIN THE RANGE FROM ABOUT 170*F. TO ABOUT 300*F. AT A SUPERFICIAL GAS VELOCITY FROM ABOUT 0.2 TO ABOUT TO ABOUT 2 FEET PER SECOND TO REDUCE THE SOLVENT CONTENT OF THE POLYMER TO LESS THAN 100 P.P.M. AND RECOVERING SAID POLYMER FROM SAID SECOND FLUIDIZED BED. 